Battery Status displays the battery levels of your Mac’s connected hardware

Editor’s note: The following review is part of Macworld’s GemFest 2012 series. Every weekday from mid June through mid August, the Macworld staff will use the Mac Gems blog to briefly cover a favorite free or low-cost program.

We’ve covered a good number of Gems that can display your laptop’s battery status in the menu bar. But Battery Status ( Mac App Store link) offers a unique twist that will appeal to Mac laptop and desktop users who also own Apple’s Magic Trackpad, Magic Mouse, or Wireless Keyboard. It offers information about the battery status of each of those devices, as well.

Battery Status’s menu icon displays a graphical representation of the battery level of one of the supported devices or, for MacBook users, your laptop’s battery level—you choose which in the app’s preferences window. Alternatively, you can choose to have the icon automatically display the level of the battery with the lowest remaining percentage of a full charge. You can also choose to display the numerical percentage next to the icon, and you can choose whether that icon should be black and white or use colors (green for a good charge, red for almost empty, and yellow for a range somewhere in the middle).

Clicking Battery Status’s menu-bar icon, and the resulting menu displays information about all your batteries. For Apple’s Bluetooth peripherals, you see the percentage charge remaining, as well as an estimate of when the battery will run out of juice. If you’ve replaced a battery since you started using Battery Status, you’ll also see the date of that change.

For MacBooks, you see the current battery percentage, how long your laptop will run on the current charge, the number of charge cycles the battery has been through, and what percentage of the original capacity the battery can currently attain at full charge. The estimates of usage time require up to a week of use with Battery Status running, as the app needs to monitor each battery long enough to generate a reliable estimate.

You can get the percentage of battery life remaining for the Magic Trackpad, Magic Mouse, and Wireless Keyboard via a submenu in Apple’s Bluetooth menu, but it’s a hassle to get to, and Battery Status offers more information. The fact that Battery Status lets you use a single menu-bar space to monitor all your batteries makes it both useful and prudent.